Torque converter impeller including impeller shell having thinned section

ABSTRACT

An impeller for a torque converter is provided. The impeller includes an impeller shell including an inner circumference, an outer circumference and a radial extension extending radially outward from the inner circumference. The radial extension includes an axially extending groove formed therein. The impeller also includes an impeller hub welded to the impeller shell by a weld. The weld is radially inside of the axially extending groove. The axially extending groove is 5 to 10 millimeters from the weld. A method of forming an impeller for a torque converter is also provided.

This claims the benefit to U.S. Provisional Patent Application No.61/876,843, filed on Sep. 12, 2013, which is hereby incorporated byreference herein.

The present disclosure relates generally to torque converters and morespecifically to impellers of torque converters.

BACKGROUND OF INVENTION

U.S. Pub. 2012/0151907 discloses method of connecting an impeller huband impeller shell.

BRIEF SUMMARY OF THE INVENTION

An impeller for a torque converter is provided. The impeller includes animpeller shell including an inner circumference, an outer circumferenceand a radial extension extending radially outward from the innercircumference. The radial extension includes an axially extending grooveformed therein. The impeller also includes an impeller hub welded to theimpeller shell by a weld. The weld is radially inside of the axiallyextending groove. The axially extending groove is 5 to 10 millimetersfrom the weld.

A method of forming an impeller for a torque converter is provided. Themethod includes providing an impeller shell including an innercircumference, an outer circumference and a radial extension extendingradially outward from the inner circumference; forming an axiallyextending groove in the radial extension; and welding an impeller hub tothe impeller shell so as to form a weld on a back surface of the radialextension. The weld is radially inside of the axially extending grooveand the axially extending groove is 5 to 10 millimeters from the weld.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described below by reference to the followingdrawings, in which:

FIG. 1 shows a schematic cross-sectional side view of a torque converterincluding an impeller in accordance with an embodiment of the presentinvention;

FIG. 2 a shows a cross-sectional side view of an impeller shell of theimpeller;

FIG. 2 b shows an enlarged view of a radial extension of the impellershell as shown in the cross-sectional side view shown in FIG. 2 a;

FIG. 2 c shows a perspective view of a back surface of the impeller;

FIG. 3 a shows a cross-sectional side view of the impeller after a frontsurface of impeller shell has been thinned; and

FIG. 3 b shows an enlarged view of the radial extension of the impellershell as shown in the cross-sectional side view shown in FIG. 3 a.

DETAILED DESCRIPTION

One embodiment of the present invention includes an impeller shellhaving a particular radius formed therein that is then machined tocreate a flexible thinned section. Testing has shown that addingflexibility to the impeller shell may improve durability of the impellerhub weld. The impeller shell is thinned by machining the back side ofthe radius to form a bearing surface.

FIG. 1 shows a schematic cross-sectional side view of a torque converter10 including an impeller 12 in accordance with an embodiment of thepresent invention. Torque converter 10 includes a cover 14 including afront cover 16 and a rear cover 18, which is formed by an impeller shell20 of impeller 12. Cover 14 houses a lockup clutch 22 and a damper 24,which are both schematically shown, and a turbine 26 opposite ofimpeller 12. Lockup clutch 22 engages with and disengages from frontcover 16 and damper 24 couples turbine 26 to lockup clutch 22 such thatturbine 26 is circumferentially driven with front cover 16 when lockupclutch 22 is engaged with front cover 16. Impeller 20 further includesan impeller hub 27 fixed to impeller shell 20 and impeller blades 36supported by a rounded portion 34 of impeller shell 20.

FIG. 2 a shows a cross-sectional side view of impeller shell 20.Impeller shell 20 includes an inner circumference 28, an outercircumference 30 and a radial extension 32 extending radially from innercircumference 28. Impeller shell 20 includes a rounded portion 34radially outside of radial extension 32. Rounded portion 34 isconfigured for supporting impeller blades 36 (FIGS. 1 and 3 a) andincludes a plurality of slots 38 formed therein for receiving blade tabsof impeller blades 36. Impeller shell 20 includes an axial extension 40radially outside of rounded portion 34 for connecting to front cover 16(FIG. 1). An outer radial surface of axial extension 40 defines outercircumference 30.

FIG. 2 b shows an enlarged view of radial extension 32 as shown in thecross-sectional side view shown in FIG. 2 a. Radial extension 32 has anaxially extending groove 42 formed in a back surface 43 of impellershell 20 for adding flexibility to impeller shell 20. Axially extendinggroove 42 also extends circumferentially. In this preferred embodiment,axially extending groove 42 is formed during the stamping of impellershell 20. In other embodiments, axially extending groove 42 may bemachined or stamping into impeller shell 20 after impeller shell 20 hasbeen formed by stamping. Radial extension 32 is substantially plateshaped and includes a flat inner radial portion 44 for connecting to animpeller hub 46 (FIG. 3 a). An inner radial surface of flat inner radialportion 44 defines inner circumference 28. Radially outward from flatinner radial portion 44, radial extension 32 protrudes slightly axiallyinward to form an intermediate portion 46. Intermediate portion 46 issubstantially flat, except for axially extending groove 42 and an axialprotrusion 48 on a front surface 50 of impeller shell 20 formed bymaterial displaced during the stamping of axially extending groove 42.Axially extending groove 42 has a curved surface, which in thispreferred embodiment has a radius of curvature R of at least 5millimeters. Axially extending groove 42 has a depth D of approximately0.8 millimeters.

FIG. 2 c shows a perspective view of the back surface 43 of impeller 12.As shown in FIG. 2 c, axially extending groove 42 is ring shaped andextends continuously circumferentially around back surface 43.

FIG. 3 a shows a cross-sectional side view of impeller 12 after frontsurface 50 of impeller shell 20 has been thinned and FIG. 3 b shows anenlarged view of radial extension 32 as shown in the cross-sectionalside view shown in FIG. 3 a. Specifically, front surface 50 has beenmachined at intermediate portion 46 to remove material from impellershell 20 opposite of axially extending groove 42. As shown in FIG. 3 b,after machining, intermediate portion 46 still protrudes slightly withrespect to flat inner radial portion 44. In this preferred embodiment,the thickness X of impeller 20 at axially extending groove 42 is atleast 1.7 millimeters after the thinning of front surface 50 of radialextension 32. After the machining, axial protrusion 48 has been removedand a machined portion 52 that is ring shaped and has a flat surface isformed. The machining adds further flexibility to impeller shell 20. Asshown in FIG. 3 a, rounded portion 34 supports a plurality of impellerblades 36.

Impeller hub 27 is welded to impeller shell 20 by a weld 54 extendingcircumferentially around impeller hub 27 at a front end 56 thereof.Front end 56 rests against back surface 43 of impeller shell 20. To adddesired flexibility to impeller shell 20, axially extending groove 42 isspaced from weld 54 by a radial distance Y that is between 5 to 10millimeters. Testing has shown that this adding of flexibility to theimpeller shell 20 improves durability of impeller hub weld 54.

In the preceding specification, the invention has been described withreference to specific exemplary embodiments and examples thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broader spirit and scope ofinvention as set forth in the claims that follow. The specification anddrawings are accordingly to be regarded in an illustrative manner ratherthan a restrictive sense.

What is claimed is:
 1. An impeller for a torque converter comprising: animpeller shell including an inner circumference, an outer circumferenceand a radial extension extending radially outward from the innercircumference, the radial extension including an axially extendinggroove formed therein; and an impeller hub welded to the impeller shellby a weld, the weld being radially inside of the axially extendinggroove, the axially extending groove being 5 to 10 millimeters from theweld.
 2. The impeller as recited in claim 1 wherein the radial extensionincludes a flat inner radial portion, the weld being formed on the flatinner radial portion, the radial extension protruding slightly axiallyinward to form an intermediate portion radially outside of the flatinner radial portion, the axially extending groove being formed in theintermediate portion.
 3. The impeller as recited in claim 1 wherein theaxially extending groove has a curved surface, the curved surface havinga radius of curvature of at least 5 millimeters.
 4. The impeller asrecited in claim 1 wherein the axially extending groove is formed as aring shaped groove extending circumferentially around the innercircumference.
 5. The impeller as recited in claim 1 wherein the axiallyextending groove is formed in a back surface of the impeller shell, theimpeller shell including a machined portion on a front surface of theradial extension opposite the axially extending groove.
 6. The impelleras recited in claim 5 wherein the radial extension includes a flat innerradial portion, the weld being formed on the flat inner radial portion,the radial extension protruding slightly axially inward to form anintermediate portion radially outside of the flat inner radial portion,the axially extending groove and the machined portion being formed inthe intermediate portion.
 7. The impeller as recited in claim 5 whereinthe machined portion is thinner than a remainder of the radialextension.
 8. The impeller as recited in claim 6 wherein the machinedportion is formed as a ring shaped flat surface.
 9. The impeller asrecited in claim I further comprising impeller blades, the impellershell including a rounded portion radially outside of the radialextension, the rounded portion supported the impeller blades.
 10. Theimpeller as recited in claim 9 wherein the impeller shell includes anaxial extension radially outside of the rounded portion for connected toa torque converter front cover, the axial extension defining the outercircumference.
 11. A torque converter comprising the impeller as recitedin claim
 1. 12. A method of forming an impeller for a torque convertercomprising: providing an impeller shell including an innercircumference, an outer circumference and a radial extension extendingradially outward from the inner circumference; forming an axiallyextending groove in the radial extension; and welding an impeller hub tothe impeller shell so as to form a weld on a back surface of the radialextension, the weld being radially inside of the axially extendinggroove, the axially extending groove being 5 to 10 millimeters from theweld.
 13. The method as recited in claim 12 wherein the radial extensionincludes a flat inner radial portion, the weld being formed on the flatinner radial portion, the radial extension protruding slightly axiallyinward to form an intermediate portion radially outside of the flatinner radial portion, the axially extending groove being formed in theintermediate portion.
 14. The method as recited in claim 12 wherein theforming the axially extending groove includes machining the axiallyextending groove into the radial extension.
 15. The method as recited inclaim 12 wherein the forming the axially extending groove includesstamping the axially extending groove into the radial extension.
 16. Themethod as recited in claim 12 wherein the axially extending groove isformed in a back surface of the impeller shell, the method furtherincluding machining a front surface of the radial extension opposite theaxially extending groove.
 17. The method as recited in claim 16 whereinthe radial extension includes a flat inner radial portion, the weldbeing formed on the flat inner radial portion, the radial extensionprotruding slightly axially inward to form an intermediate portionradially outside of the flat inner radial portion, the axially extendinggroove being formed in a back surface of the intermediate portion, themachining including machining a front surface of the intermediateportion.
 18. The method as recited in claim 16 wherein after the formingthe axially extending groove and machining the front surface, the radialextension has a thickness of at least 1.7 millimeters at the axiallyextending groove.
 19. The method as recited in claim 12 wherein theaxially extending groove has a curved surface, the curved surface havinga radius of curvature of at least 5 millimeters.
 20. The method asrecited in claim 12 wherein the axially extending groove is formed as aring shaped groove extending circumferentially around the innercircumference.